Results of clonogenic survival experiments (n = 3) for each pancreatic cancer cell line after exposure to SFN in a low (2 μM, for MIA PaCa-2 only 1 μM) or high dose (10 μM, for MIA PaCa-2 only 5 μM) for 24 h followed by RT in a low (2 Gy) or high dose (6 Gy), and combination of both. (A) Survival grouped by treatments including Students t-test statistics (* p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001). (B) Logarithmic survival as function of dose for radiation and co-treatments as well as calculated artificial theoretical control curves of assumed isoeffective radiation doses for low (dotted) and high dose SFN (dashed), respectively. Co-treatments with a surviving fraction below the respective theoretical control curve can be considered as supra-additive (see materials and methods section).